Here's a silly definition: A number is a sequence of 1 or more digits, optionally beginning with a '-' and optionally followed by a '.' and one or more digits,

Here's a silly definition: A number is a sequence of 1 or more digits, optionally beginning with a '-' and optionally followed by a '.' and one or more digits, where digits are the characters {'0' '1' '2' '3' '4' '5' '6' '7' '8' '9'}. Examples: 1, 25, 3.2, -8 "1 + 2" is not a number, but its evaluation is